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post #1 of 4 (permalink) Old 11-19-2017, 11:54 AM Thread Starter
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Smile Head torque setting.

I have a slight oil leak from the cylinder head gasket on my 350 Ipotesi. Can anyone tell me the torque figure for tightening the head down to see if that is the problem.


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Steve.
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post #2 of 4 (permalink) Old 11-22-2017, 01:06 PM
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Hi Steve,
I don't know the exact answer to your question but as no-one has replied, I thought I'd tell what I would do.
First, I'd measure the diameter of the thread / bolt shank with a vernier caliper to determine the head bolt size. Most likely they will be metric M8 or M10. If they are bolts and you can't get to the shank without removing one then the spanner size will tell you - M8 is 13mm spanner, M10 is 16mm spanner, M12 is 18mm spanner.
The next thing is to find out the grade of steel the bolt is made from. Cylinder head bolts are usually 8.8 but could be 12.9. This should be marked on the head of the bolt.
Then look at the chart I've attached for the suggested torque. I'd use the torque for dry unlubricated threads.
Just one other point. On chain driven OHC engines the cam timing changes a little when the head is re-torqued, as the head gasket can compresses a little more. This most likely won't be a problem for you but some engines can be quite sensitive to this, in which case the cam timing would need to be reset (on my CS175 for example!)
Hope this helps.
Ron
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Last edited by Mondello175; 11-22-2017 at 02:34 PM.
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post #3 of 4 (permalink) Old 11-23-2017, 01:47 PM Thread Starter
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Hello Ron.
Many thanks for your input, As I had no replies I got a torque wrench and set it at 20 foot pounds and one of the 8mm studs tightened a little, then I tried 25 and that stud and another tightened a little and then I went to 30 and all except one tightened slightly and I think that agrees with the table you sent me.
I cannot see the tensile strength because they are studs and not bolts but as they are only 8mm I think they must be fairly high tensile.
I will run it and see if it has cured the problem.
Just one more point and that is as the valves are pushrod operated I had to adjust the valve clearances as they had gone to nothing so I think the head has definitely gone down.

Regards.
Steve.
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post #4 of 4 (permalink) Old 11-24-2017, 05:54 AM
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No problem Steve.
The oil leak is most likely from where the oil gallery passes through the head gasket. They usually have an O ring so the extra compression may just be enough to seal - let's hope so.
Ron
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